Rock Hard Ten shed a frog on his right front foot following Friday morning's workout. He had suffered a bruise on his left front foot after a workout Oct. 20 at Santa Anita and Mandella said that injury had improved with treatment.
Though Mandella said the injury to the 4-year-old colt's right front foot is "fairly minor ... It's very tender. We can't run him."
Rock Hard Ten had been the second favorite on the morning line at 7-2 behind Saint Liam (3-1) for Saturday's race.
Mandella spotted blood on Rock Hard Ten's heel following a 5/8-mile gallop early Friday.
"The frog started to loosen last week and shed during the gallop," said Mandella. He described the frog as "the cushion between the two heels on the foot that is like a shock absorber. It's the first thing that meets the ground."
Mandella said though he's disappointed the colt won't be running Saturday he's "thankful it happened here and not on the track (during a race), when he could have broken a leg or gotten hurt badly.